Screw Compressor System for a Utility Vehicle

ABSTRACT

A screw compressor system for a utility vehicle has at least one screw compressor, at least one screw compressor drive with an output shaft, at least one driven screw with a screw drive shaft section. The output shaft and the screw drive shaft section are essentially coaxial.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No. PCT/EP2017/073543, filed Sep. 19, 2017, which claims priority under 35 U.S.C. § 119 from German Patent Application No. 10 2016 011 433.9, filed Sep. 21, 2016, the entire disclosures of which are herein expressly incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a screw compressor system for a utility vehicle, having at least one screw compressor, at least one screw compressor drive with an output shaft, and with at least one driven screw.

Screw compressors for utility vehicles are already known from the prior art. Such screw compressors are used to provide the compressed air required for the brake system of the utility vehicle, for example.

In this context, in particular oil-filled compressors, in particular also screw compressors, are known, in the case of which it is necessary to regulate the oil temperature. This is generally realized by virtue of an external oil cooler being provided which is connected to the oil-filled compressor and to the oil circuit via a thermostat valve. Here, the oil cooler is a heat exchanger which has two mutually separate circuits, wherein the first circuit is provided for the hot liquid, that is to say the compressor oil, and the second circuit is provided for the cooling liquid. As cooling liquid, use may, for example, be made of air, water mixtures with an antifreeze, or another oil.

This oil cooler must then be connected to the compressor oil circuit by means of pipes or hoses, and the oil circuit must be safeguarded against leakage.

This external volume must furthermore be filled with oil, such that the total quantity of oil is also increased. The system inertia is thus increased. Furthermore, the oil cooler must be mechanically accommodated and fastened, either by way of brackets situated in the surroundings or by way of a separate bracket, which necessitates additional fastening means and also structural space.

It is the object of the present invention to advantageously further develop a screw compressor system for a utility vehicle of the type mentioned in the introduction, in particular such that the mounting of the screws of the screw compressor can be simplified and made less expensive, and such that the screw compressor can be designed to be of smaller construction.

This object is achieved by a screw compressor system for a utility vehicle having the claimed features. Provision is made for the screw compressor system for the utility vehicle to be equipped with at least one screw compressor, at least one screw compressor drive with an output shaft, and at least one driven screw with a screw drive shaft portion. The output shaft and the screw drive shaft portion are substantially coaxial.

The invention is based on the underlying concept of considerably reducing the acting radial forces and radial moments by way of a coaxial transmission of torque between screw compressor drive and the driven screw, such that, substantially, aside from the drive torque, considerably lower radial forces arise than for example in the case of screws of a screw compressor that are driven by toothed gear stages or belt drives. It is thereby made possible to use smaller bearings, and for these to also be able to be designed for lower acting forces and moments.

Through the use of relatively small bearings, it is also made possible for the screw compressor to be able to be of a smaller and more compact construction. The manufacture of the bearing seats in the housing of the screw compressor is also simplified in this way. It is thus made possible for the manufacturing costs of the screw compressor to be considerably reduced. By use of smaller bearings, the tolerance chain is furthermore made shorter, and altogether higher accuracy is achieved in terms of manufacturing and assembly.

In particular, provision may be made for a compensating coupling to be provided between the output shaft and the screw drive shaft portion. The acting radial forces can be reduced by way of the compensating coupling. Furthermore, it is also possible for a slight offset between the output shaft and the screw drive shaft portion to be compensated. In this way, it is made possible to likewise shorten the tolerance chain and also improve the assembly process. A reduction in wear can also be achieved in this way.

The screw drive shaft portion may have a first bearing portion. Mounting of the screw may be performed at this bearing portion. In this way, it is also made possible for the driven screw to be mounted in a manner suited to the occurring loads.

In particular, provision may be made for a radial bearing to be arranged in the first bearing portion. Here, from experience, it is not necessary for axial forces to be accommodated, such that the arrangement of a radial bearing is sufficient. In this way, the structural space required for the bearing at this location can be selected to be smaller, and is also possible for a bearing seat in the housing to be provided with smaller diameters. This likewise makes it easier to shorten the tolerance chain and achieve higher levels of accuracy.

The radial bearing may be in the form of a needle-roller bearing. By means of the arrangement as a needle-roller bearing, an inexpensive bearing type is selected which is at the same time suited to the occurring loads.

In particular, provision may furthermore be made for the radial bearing to have no inner ring. It is thus achieved that, overall, the outer diameter of the bearing can be selected to be smaller.

In this context, provision may be made in particular for the rolling elements of the radial bearing to run directly on the surface of the first bearing portion.

The first bearing portion may in this case be correspondingly hardened and formed as a bearing seat. By means of the direct rolling contact of the rolling elements with the surface of the first bearing portion, it is made possible to be able to provide an altogether smaller construction, and also to realize less expensive production. Through the omission of the inner ring of the radial bearing, altogether smaller diameters are required for the bearings.

Furthermore, provision may be made for the driven screw to also have a screw portion and a second bearing portion in addition to the screw drive shaft portion, wherein the screw portion is situated between the screw drive shaft portion and the second bearing portion. Thus, the screw portion is arranged between the screw drive shaft portion and the second bearing portion, and the screw is thus mounted at both ends.

In this context, provision may be made in particular for the screw drive shaft portion to have a bearing seat on the side facing toward the screw portion and to have the attachment piece for the compensating coupling on the side averted from the screw portion.

A bearing for accommodating axial and radial forces may be arranged on the second bearing portion. By means of this bearing arrangement, it is made possible for the occurring loads of the bearing is to be accommodated in a useful and expedient manner. The relatively large dimensions of the bearing that are possibly required here can also be more easily accommodated in the housing at this location.

Furthermore, provision may be made for the screw that meshes with the driven screw to have a substantially identical bearing arrangement to the driven screw.

The manufacturing process is hereby simplified. Furthermore, identical tools can be used for forming the bearing seats in the housing. It is thus possible for the changeover times in the production process to be reduced.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional drawing through an exemplary screw compressor according to the invention.

FIG. 2 is a perspective plan view of the screws of the screw compressor with corresponding bearing arrangement and compensating coupling.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in a schematic sectional illustration, a screw compressor 10 in the context of an exemplary embodiment of the present invention.

The screw compressor 10 has a fastening flange 12 for the mechanical fastening of the screw compressor 10 to an electric motor (not shown in any more detail here).

What is shown, however, is the input shaft 14, by which the torque from the electric motor is transmitted to one of the two screws 16 and 18, specifically the screw 16.

The screw 18 meshes with the screw 16 and is driven by means of the latter.

The screw compressor 10 has a housing 20 in which the main components of the screw compressor 10 are accommodated.

The housing 20 is filled with oil 22.

At the air inlet side, an inlet connector 24 is provided on the housing 20 of the screw compressor 10. The inlet connector 24 is in this case designed such that an air filter 26 is arranged at the inlet connector. Furthermore, an air inlet 28 is provided radially on the air inlet connector 24.

In the region between the inlet connector 24 and the point at which the inlet connector 24 joins to the housing 20, there is provided a spring-loaded valve insert 30, which is designed here as an axial seal.

The valve insert 30 serves as a check valve.

Downstream of the valve insert 30, an air feed channel 32 is provided which feeds the air to the two screws 16, 18.

At the outlet side of the two screws 16, 18, an air outlet pipe 34 with a riser line 36 is provided.

In the region of the end of the riser line 36, a temperature sensor 38 is provided by which the oil temperature can be monitored.

Also provided in the air outlet region is a holder 40 for an air deoiling element 42.

In the assembled state, the holder 40 for the air deoiling element has the air deoiling element 42 in the region facing toward the base (as also shown in FIG. 1).

Also provided, in the interior of the air deoiling element 42, is a corresponding filter screen or known filter and oil separating devices 44, which will not be specified in any more detail.

In the central upper region in relation to the assembled and operationally ready state (that is to say as shown in FIG. 1), the holder 40 for the air deoiling element 42 has an air outlet opening 46 which leads to a check valve 48 and a minimum pressure valve 50. The check valve 48 and the minimum pressure valve 50 may also be formed in one common combined valve.

The air outlet 51 is provided downstream of the check valve 48.

The air outlet 51 is generally connected to correspondingly known compressed-air consumers.

In order for the oil 22 that is situated and separated off in the air deoiling element to be returned into the housing 20, a riser line 52 is provided which has a filter and check valve 54 at the outlet of the holder 40 for the air deoiling element 42 at the transition into the housing 20.

A nozzle 56 is provided, downstream of the filter and check valve 54, in a housing bore. The oil return line 58 leads back into approximately the central region of the screw 16 or of the screw 18 in order to feed oil 22 thereto again.

An oil drain screw 59 is provided in the base region, in the assembled state, of the housing 20. By way of the oil drain screw 59, a corresponding oil outflow opening can be opened, via which the oil 22 can be drained.

Also provided in the lower region of the housing 20 is the attachment piece 60 to which the oil filter 62 is fastened. Via an oil filter inlet channel 64, which is arranged in the housing 20, the oil 22 is conducted firstly to a thermostat valve 66.

Instead of the thermostat valve 66, it is also possible for an open-loop and/or closed-loop control device to be provided by which the oil temperature of the oil 22 situated in the housing 20 can be monitored and set to a setpoint value.

Located downstream of the thermostat valve 66 is the oil inlet of the oil filter 62, which, via a central return line 68, conducts the oil 22 back to the screw 18 or to the screw 16 again, and also to the oil-lubricated bearing 70 of the shaft 14. Also provided in the region of the bearing 70 is a nozzle 72, which is provided in the housing 20 in conjunction with the return line 68.

The cooler 74 is connected to the attachment piece 60.

In the upper region of the housing 20 (in relation to the assembled state), a safety valve 76 is located, by which an excessively high pressure in the housing 20 can be dissipated.

Upstream of the minimum pressure valve 50, a bypass line 78 is located, which leads to a relief valve 80. Via said relief valve 80, which is activated by means of a connection to the air feed 32, air can be returned into the region of the air inlet 28. In this region, there may be provided a ventilation valve (not shown in any more detail) and also a nozzle (diameter constriction of the feeding line).

Furthermore, approximately at the level of the line 34, an oil level sensor 82 may be provided in the outer wall of the housing 20. The oil level sensor 82 may for example be an optical sensor, and may be designed and configured such that, on the basis of the sensor signal, it can be identified whether the oil level during operation is above the oil level sensor 82 or whether the oil level sensor 82 is exposed, and thus the oil level has correspondingly fallen.

In conjunction with this monitoring, it is also possible for an alarm unit to be provided which outputs or transmits a corresponding error message or warning message to the user of the system.

The function of the screw compressor 10 shown in FIG. 1 is as follows.

Air is fed via the air inlet 28 and passes via the check valve 30 to the screws 16, 18, where the air is compressed. The compressed air-oil mixture, which, having been compressed by a factor of between 5 and 16 downstream of the screws 16 and 18, rises through the outlet line 34 via the riser pipe 36, and is blown directly onto the temperature sensor 38.

The air, which still partially carries oil particles, is then conducted via the holder 40 into the air deoiling element 42 and, if the corresponding minimum pressure is attained, passes into the air outlet line 51.

The oil 22 situated in the housing 20 is kept at operating temperature via the oil filter 62 and possibly via the heat exchanger 74.

If no cooling is necessary, the heat exchanger 74 is not used and is also not activated.

The corresponding activation is performed by way of the thermostat valve 68. After purification in the oil filter 64, oil is fed via the line 68 to the screw 18 or to the screw 16, and also to the bearing 72. The screw 16 or the screw 18 is supplied with oil 22 via the return line 52, 58, and the purification of the oil 22 takes place here in the air deoiling element 42.

By use of the electric motor (not shown in any more detail), which transmits its torque via the shaft 14 to the screw 16, which in turn meshes with the shaft 18, the screws 16 and 18 of the screw compressor 10 are driven.

By use of the relief valve 80 (not shown in any more detail), it is ensured that the high pressure that prevails for example at the outlet side of the screws 16, 18 in the operational state cannot be enclosed in the region of the feed line 32, and that, instead, in particular during the start-up of the compressor, there is always a low inlet pressure, in particular atmospheric pressure, prevailing in the region of the feed line 32. Otherwise, upon a start-up of the compressor, a very high pressure would initially be generated at the outlet side of the screws 16 and 18, which would overload the drive motor.

FIG. 2 shows, in a perspective view, the driven screw 16 and the screw 18, which meshes with the driven screw, of the screw compressor system 100 for a utility vehicle. The screw compressor system 100 for the utility vehicle has the screw compressor 10 as shown in FIG. 1 and an electric motor (not illustrated in any more detail) as a drive.

The input shaft 14 corresponds substantially to the screw drive shaft portion of the screw 16 and has a screw drive shaft portion 102.

The screw drive shaft portion 102 and the output shaft (not shown in any more detail) of the screw compressor drive, in this case for example an electric motor, are coaxial with respect to one another.

This can be seen in FIG. 2 by virtue of the compensating coupling 104 being shown.

The compensating coupling 104 is seated on the end of the screw drive shaft portion 102 and also on the end of the output shaft of the screw compressor drive.

The screw drive shaft portion 102 furthermore has a first bearing portion 106, which has an identical diameter to the screw drive shaft portion 102 as a whole. At this location, however, the screw drive shaft portion 102 is hardened, because the first bearing portion 106 is provided there for the arrangement of a bearing.

At the first bearing portion 106, a radial bearing 108 is arranged, wherein the radial bearing 108 is formed here as a needle-roller bearing.

Here, the radial bearing 108 has no inner ring, and the rolling elements, that is to say the needles of the radial bearing 108, run directly on the surface of the first bearing portion 106.

The driven screw 16 also has a screw portion 110 and a second bearing portion 112 in addition to the screw drive shaft portion 102.

Here, the screw portion 110 is arranged between the screw drive shaft portion 102 and the second bearing portion 112.

Here, a bearing 114 for accommodating radial and axial forces is arranged in the second bearing portion 112. It is thus possible for the forces acting on the driven screw 16 to be able to be accommodated by way of a radial/axial bearing of relatively small construction. On the screw drive shaft portion 102 situated between screw portion 110 and the compensating coupling 104, it is entirely adequate for only radial forces to be accommodated there.

Adequate mounting of the driven screw 16 is thus made possible.

It is thus possible for a smaller construction to be provided, and it is no longer necessary for relatively large bearings 114 for accommodating the acting radial forces to be provided as in the case, for example, of a drive with a belt drive or with a toothed gear stage.

The screw 18 which, by means of the driven screw 16, meshes with the latter has substantially an identical bearing arrangement to the driven screw 16.

In this way, it is made possible for the bearing seats in the housing 20 to be able to be formed substantially with identical diameters. In this way, the changeover times of the tools to be used are reduced. Here, too, relatively little structural space is required.

LIST OF REFERENCE SIGNS

-   10 Screw compressor -   12 Fastening flange -   14 Input shaft -   16 Screws -   18 Screws -   20 Housing -   22 Oil -   24 Inlet connector -   26 Air filter -   28 Air inlet -   30 Valve insert -   32 Air feed channel -   34 Air outlet pipe -   36 Riser line -   38 Temperature sensor -   40 Holder for an air deoiling element -   42 Air deoiling element -   44 Filter screen or known filter or oil separation devices -   46 Air outlet opening -   48 Check valve -   50 Minimum pressure valve -   51 Air outlet -   52 Riser line -   54 Filter and check valve -   56 Nozzle -   58 Oil return line -   59 Oil drain screw -   60 Attachment piece -   60 a Outer ring -   60 b Inner ring -   62 Oil filter -   64 Oil filter inlet channel -   66 Thermostat valve -   68 Return line -   70 Bearing -   72 Nozzle -   74 Cooler, heat exchanger -   76 Safety valve -   78 Bypass line -   80 Relief valve -   82 Oil level sensor -   100 Screw compressor system -   102 Screw drive shaft portion -   104 Compensating coupling -   106 First bearing portion -   108 Radial bearing -   110 Screw portion -   112 Second bearing portion -   114 Bearing

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

What is claimed is:
 1. A screw compressor system for a utility vehicle, comprising: at least one screw compressor; at least one screw compressor drive with an output shaft; and at least one driven screw with a screw drive shaft portion, wherein the output shaft and the screw drive shaft portion are substantially coaxial.
 2. The screw compressor system as claimed in claim 1, wherein a compensating coupling is provided between the output shaft and the screw drive shaft portion.
 3. The screw compressor system as claimed in claim 1, wherein the screw drive shaft portion has a first bearing portion.
 4. The screw compressor system as claimed in claim 3, wherein a radial bearing is arranged on the first bearing portion.
 5. The screw compressor system as claimed in claim 4, wherein the radial bearing is in the form of a needle-roller bearing.
 6. The screw compressor system as claimed in claim 4, wherein the radial bearing has no inner ring.
 7. The screw compressor system as claimed in claim 4, wherein rolling elements of the radial bearing run directly on a surface of the first bearing portion.
 8. The screw compressor system as claimed in claim 5, wherein rolling elements of the radial bearing run directly on a surface of the first bearing portion.
 9. The screw compressor system as claimed in claim 6, wherein rolling elements of the radial bearing run directly on a surface of the first bearing portion.
 10. The screw compressor system as claimed in claim 3, wherein the driven screw has a screw portion and a second bearing portion in addition to the screw drive shaft portion, and the screw portion is situated between the screw drive shaft portion and the second bearing portion.
 11. The screw compressor system as claimed in claim 10, wherein a bearing for accommodating axial and radial forces is arranged on the second bearing portion.
 12. The screw compressor system as claimed in claim 1, wherein a further screw that meshes with the driven screw has a substantially identical bearing arrangement to the driven screw.
 13. The screw compressor system as claimed in claim 11, wherein a further screw that meshes with the driven screw has a substantially identical bearing arrangement to the driven screw. 